The US military blamed the Islamic State (IS) group for the death of more than 100 civilians in Iraq’s northern city of Mosul in a March airstrike by coalition forces.

The airstrike on March 17 against two IS snipers ignited a large amount of explosive material the group had placed in the structure, where 101 civilians were sheltered, the US Defense Department said in a statement on Thursday.

Neither Coalition nor Iraqi forces knew that civilians were sheltered within the structure, the statement said, adding that an additional 36 civilians who were reported to be connected to the structure remain unaccounted for, Xinhua news agency reported.

“Our condolences go out to all those that were affected,” said US Major General Joe Martin, the commanding general of coalition forces.

“The Coalition takes every feasible measure to protect civilians from harm. The best way to protect civilians is to defeat ISIS,” the general said, using an alternate acronym for the group.

The US Defense Department said in April that at least 352 civilians were killed as a result of US-led campaign against the IS in Iraq and Syria from August 2014 to March 2017. The figure is lower than the estimation of monitoring groups.